The present disclosure relates to an electrostatic latent image developing toner and a method for producing an electrostatic latent image developing toner.
In electrophotography, a high quality image is generally obtained as follows: First, the surface of a photoconductive drum is charged by using corona discharge or the like, and an electrostatic latent image is formed thereon by exposure with a laser or the like. The thus formed electrostatic latent image is developed by a toner to form a toner image. Ultimately, the thus formed toner image is transferred onto a recording medium. In general, a toner containing toner particles (toner mother particles) having an average particles size of 5 μm or more and 10 μm or less is used as the toner for forming such a toner image. In order to obtain such a toner, a mixture of a binder resin such as a thermoplastic resin and a component such as a coloring agent, a charge control agent or a release agent is subjected to a kneading process, a pulverizing process and a classifying process. This production method for a toner including the kneading of a material, the pulverizing of the kneaded product and the classification of the ground product is generally designated as a “pulverizing method”. Besides, an inorganic powder of silica or titanium oxide is externally added to the toner mother particles. Thus, the resultant toner can be provided with fluidity and suitable charge performance, and a cleaning property of removing the toner from the photoconductive drum can be improved.
From the viewpoint of energy saving or downsizing of an apparatus, this type of toner is desired to have such excellent low-temperature fixability that it can be satisfactorily fixed without heating a fixing roller to the utmost. A toner having excellent low-temperature fixability, however, easily aggregates in general because most of such toners use a binder resin having a low melting point or a low glass transition point, or a release agent having a low melting point. If the toner aggregates, it is apprehended that an image defect due to adhesion of the toner onto a developing sleeve or a photoconductive drum, or fogging due to insufficient charging of the toner may be caused in forming an image.
In order to overcome this problem, a toner including toner particles with hardness, determined by using a displacement of elasticity, falling in a specific range, has been proposed. The elastic displacement is obtained on the basis of a displacement caused by applying stress and a displacement caused by removing the stress, and corresponds to a degree of plastic displacement of a toner particle.